1. Field of the Invention
This invention relates to a fibrous structure for reinforcing a composite material and a method of manufacturing the fibrous structure.
2. Prior Art
In the manufacture of mechanical devices required to have high strength for spacecraft, aircraft, automobiles, trains, marine craft and the like, fiber-reinforced composite materials made up of synthetic resins combined with various fibrous structures such as carbon fibers, glass fibers, aramid fibers, etc. have been utilized.
Composite materials reinforced by such fibrous structures are not only lightweight but are high in specific strength, specific rigidity and heat resistance, so that they have great value not only in the above-mentioned applications but also in many other industrial fields. The strength characteristics of such composite materials are largely dependent on the fiber content, weave and construction, matrix and the like of the fibrous structure used as a reinforcement. Methods for the manufacture of such fibrous structures have been disclosed, for example, in Japanese Laid-Open Patent Application (Kokai) Nos. 61-201063 and 59-71457, Japanese Laid-open Utility Model Application (Kokai) No. 61-37930 and other literature.
However, the known technology can be applied only when fibrous structures are comparatively simple in profile or configuration and only when various portions of each fibrous structure are comparatively uniform in fiber density. Moreover, in the manufacture of a fibrous structure having an intricate profile, a cutting operation must be performed which may cause breakage of fibers leading to reduced strength. Also, the known technology does not provide a usable means for manufacturing a bottomed hollow element, i.e., a hollow member having a bottom wall, and when it is desired to assure a large reinforcing effect in a selected direction, it is necessary to increase the strength of the entire fibrous structure, so that the resulting fibrous structure has the disadvantage of increased weight. Moreover, in forming an article having corners using a laminated fabric material, the resin forms pools in the corners which causes a decrease in strength or a sacrifice of strength at the joints.
It is an object of this invention, therefore, to provide a fibrous structure for reinforcing a composite material having a complicated profile, particularly a bottomed hollow pillar-shaped element having lateral projections such as fins, and which is capable of displaying high strength in a selected direction and is free of any remarkable fiber breakage or resin pools.